Incandescent lamp



g 20, 1940- G. B. DAVIS 2,211,884

INCANDESCENT LAMP Filed Sept. 8, 1938 Patented Aug. 20, 1940 UNITEDSTATES PATENT orrlc's" Claims.

This invention relates to an incandescentlamp to be used exclusively ina series hookup. The lamp'embodies a shunt mechanism for automaticallyestablishing circuit to the remaining lights in the series upon therupturing of the filament in the globe.

Another object of the invention is to provide a globe proficient andsafe in its operation, yet of such simple construction as to make itpractical for ornamental purposes where the cost of manufacturing is amajor consideration.

Another object is to provide a globe safe from the fire hazardaccompanying globes of this type. In all globes of this nature, hookedup in a series, as a globe burns out the voltage is increasedproportionally to the remaining lights in line. This overloading willcause them to deteriorate more rapidly and the failure of each in turnwill so increase the voltage that the last two or three globes to remainin operation will flare up and burn out simultaneously, and in so doing,set up a complete circuit through the shunt systems. The result in thiscase is either a ruptured house plug-fuse or a fire at the globe. Insome instances where globes of this type were used, a globe capable ofcarrying the entire load has been hooked up in the series so as toabsorb the excess current. I believe I have, by placing the shuntmechanism Within the globe and making it of such material as to ruptureat a comparatively low voltage, eliminated this danger.

Provisions have been made for locating the shunt within the shell capand insulating it from the same, but this method does not lend itself tobe as safe as that formerly discussed, where the shunt is sealed withinthe globe.

In order that this invention may be more fully understood reference willbe had to the accompanying drawing:

Fig. I: A sectional view of the lamp with the invention located withinthe globe.

Fig. II: A sectional View of a lamp with the shunt mechanism in theshell-cap.

Fig. III: A sectional view of a lamp with the shunt obtained by twistingtogether the oxidized lead in wires within the globe.

Fig. IV: A sectional view of the lamp with the shunt obtained bytwisting together the oxidized lead in wires beneath the globe.

Fig. V: A detail view of how an insulated fuse material may be used.

The lamp illustrated in Fig. I comprises an envelope l. Within thisenvelope is the regular filament supported by lead-in wires 3 and 4.These lead-in wires are oxidized or covered with any suitable insulationbefore being wound about by wires 1 as illustrated. Glass beads 5 and 6are merely for supports to prevent the warping of the lead-in wires awayfrom the engaging shunt wire I. Should it prove to be an advantage, wireI 5 could be insulated instead of the lead-in wires 3 and 4. A verysatisfactory insulation for this purpose can be obtained by oxidizingthe metal, or by a very thin coating of insulating varnish.

The connecting wire I can be made of very small 10 copper wire or aslightly heavier tungsten wire, either will carry suificient voltage tosupport the lights in the series but will rupture at line voltage, andat a definitely lower amperage than the house plug fuse.

The globe illustrated in Fig. II is substantially the same as thatdescribed in Fig. I, Varying in that the lead-in wires 8 and 9 have beenwrapped beneath the globe at it. Support bead H is suspended in theshell cap and insulating sleeve i2 type of globe the standard supportwire now in use will rupture at about 3 amps, but should it benecessary, supports would be made of any size or alloy to conform to anyrequirements. Precaution may be taken to prevent a rupture taking placebeneath the globe by dipping the outer extending leads in lead. Theadditional coating will increase their capacity sufficiently to assure arupture at the point desired.

In Fig. IV the wrapping of the leads takes place beneath the globe atpoint it. In this case insulating sleeve II is inserted within the shellcap to prevent shorting with the shell.

Fig. V carries out the same principle as that brought out in Fig. I,Varying in that a strip E8 of oxidized or insulated fuse material isused in- 4.5

stead of the wire. In this illustration H3 is simply folded overlead-ins l9 and 26 and supporting beads 2| and 22 hold the leads firmlyin place to prevent warping or shaking out of contact with In theoperation of this globe, current flows normally through the filamentfollowing the .course of least resistance, but upon the rupturing ofsaid filament the voltage pressure is so increased across the shuntmechanism that the seption of a pair of leads having portions thereofjuxtapositioned, a fuse strip wound around said leads but insulatedtherefrom.

3. An incandescent lamp, leads to said lamp, metallic oxide surroundingsaid leads, a fuse strip wound around said oxidized leads.

4. An incandescent lamp, lead in conductors to said lamp, a fuse stripWound around said leads, said fuse strip insulated from one only of saidleads.

5. An incandescent lamp, leads to said lamp, oxide insulationsurrounding one only of said leads, a fuse strip wound around saidleads.

GEORGE B. DAVIS.

